The purpose of this project is to study the relationship between phenylethanolamine N-methyltransferase (PNMT) levels and blood pressure control in hypertensive and normotensive rats. PNMT catalyzes the final step in catecholamine biosynthesis and is both centrally and peripherally located. Recent studies have shown that brain PNMT levels are significantly elevated in hypertensive animals when compared to their controls. Inhibition of this enzyme, particularly in the rich catecholamine containing A1 and A2 nuclei of the brainstem, is associated with significant reductions in blood pressure in hypertensive rats. These findings suggest a possible involvement of central noradrenergic neurons in blood pressure regulation as well as a possible involvement of this enzyme in the development of the hypertensive state.